Method of making camber member and thrust plate blanks for hollow metal aircraft propeller blades



J. H. MCKEE Nov. 18, 1941.

METHOD oF MAKING GAMBER MEM Ms m DLLB am SLl AFF

BRT. T i AF L A T E M 5 AShee'bs--Sheelz 1 Nov. 1s, 1941. J. H 2,263,425

MGKEE METHOD OF MAKING CAMBER MEMBER AND THRUST PLATE BLANKS FOR HOLLOWk METAL AIRCRAFT PROPELLER BLADES y Filed Feb. 17, 1939 3 Sheets-Sheet 3 Patented Nov. 18, ,41941 METHOD F MAKING CAMBER MEMBER AND THRUST PLATE BLANKS FOR HOL- LOW METAL AIRCRAFT PROPELLER BLADES James H. McKee, Pittsbnrgh,.la., assignor, by

mesne assignments, to Curtiss-Wright Corporation, New York, N. Y., a corporation of Dela- Ware Application February 17, 1939, Serial No. 256,930

9 Claims.

'I'his invention relates to hollow metal blades for aircraft propellers and more particularly to a method of making camber member andthrust plate blanks for use in the manufacture of such hollow metal blades.

In an application heretofore filed by me and serially numbered 74,007, I disclose two improv'ed forms of hollow metal blades of the' type shown in T. A. Dicks Patent No. 1,713,500 of May 14, 1929. In one of these forms, both the camber and thrust plate members at all stations between the shank of the blade and the blade tip are of uniform thickness throughout the major portion of their width but are of materially increased thickness adjacent their edges. In other Words, each of these members has bounding edge portions which are materially thicker than the ntervening body portion thereof. The change in section from the body portion to the edge portions is more or less gradual.

In Patent No. 2,214,338 issued to me on September 10, 1940, I disclose a method of making camber member and thrust plate blanks for such a blade. In such method, each of the relatively thin metal plates from which the camber member and thrust plate blanks are made, after being longitudinally tapered, is pulled down or tensioned over a milling plate which serves as a backing member and which is provided with a flat substantially horizontal central area with the portions on each side of such area inclined downwardly away from the same. 'I'he outline of the flat area approximates the outline of the member (camber membe'r or thrust plate) to be produced, but is materially smaller than said member, since the outline is the same in size and shape as the body portion of the blank located Within the thick bordering edge portions plus the portion which connects said body and edge portions above referred to.

The pulling down or tensioning procedure is preparatory to taking a straight milling cut throughout the length and breadth of that portion ofthe plate which lies above said fiat area of the backing member and it is of the utmost importance that a metal-to-metal contact is obtained between the plate and the upper flat surface of the backing member before the milling cut is made. Y

The plates used in making these blanks are stiff, and I have found that even though relatively great force vis used in pulling the same down over the backing member, it has been impossible to obtain the necessary metal-to-metal (Cl. 2li-156.8)

hammer blows are resorted to in an attempt to obtain this metal-to-metal contact, the results are not satisfactory. It-will be apparent that if this midsection does not contact at all points Awith the central at surface of the backing member, the product resulting from the subsequent milling operation will not be satisfactory, since the body portion between the thick edge portions will be of uneven thickness.

An object of this invention is to provide an improved method of 4making camber member and thrust plate blanks such as disclosed in my said applications.

Another object is to provide a simple and reliable method of making camber member and thrust plate blanks having throughout at least the major part of their length, edge portions which are materially thicker than the body portion of the blank intermediate such edge portions and with such body portions of uniform thickness transversely of the blank.

A further object is to provide a stepintermediate the longitudinal tapering and tensioning steps of the method of my application Ser. No. 84,698 which will so condition the plate that the tensioning step is effective in giving to the plate the desired surface contour.

A further object is to provide a method of treating a tapered plate of my application Ser. No. 84,698 so that such plate when tensioned against the milling plate or backing member having a flat upper surface,`will\\cause that portion of the plate above said surface to make a metalto-metal contact therewith throughout the entire area of such surface.

A further object is to provide a method of making camber member blanks having bounding edge portions which are materially thicker than the body of the blank intermediate such edge portions and in which such edge portion extends around the tip forming part of the blank as well as along its longitudinally extending edges.

These and other objects which will be apparent to those skilled in this particular art, I attain by means of the method described and illustrated in the specification and drawings accompanying and forming part of this application.

In the drawings, Figure 1 is a top plan view of a relatively thin metal plate from which to form a camber memberV blank. The dotted outline represents the outline of the camber member blank to be punched therefrom after such plate has been processed in accordance with this incontact referred to. I nd that even when heavy vention to provide the same withthe desired surface contour These views are taken on lines of Fig. 15 so far as the backing member or mill- Fig. 2 is a top plan view of a smaller relatively thin metal plate from which to form a thrust plate blank. The dotted outline in this figure represents the outlineof the thrustplate blank to be punched therefrom after such plate has been processed in accordance with this invention to provide the same with the desired surface contour;

Fig. 3 is a transverse section of a press (with a blank shown therein) such as may be utilized in transversely bending or arching such tapered plates along a'longitudinally extending central or midsection thereof; y

Fig. 4 is a perspective View of the blank oi Fig. 1 after the same has been provided with a transversely bent o r arched longitudinally extending central or midsection;

Figs. 5-14 inclusive are transverse sections taken on lines 5-5 to lines |4--I4 inclusive of Fig. 4;

Fig. is a top plan view of a backing member or milling plate against which the tapered and transversely bent or arched plate may be tensioned preparatory to the milling operation which reduces the thickness of an intermediate part of the body of the blank, thereby producing the relatively thick edge portions of the camber member andthrust plate blanks. This backing member constitutes a milling plate and is adapted to be secured to the top of the reciprocating bed of a milling machine:

Fig. 16 is a sectional view of such backing member or milling plate taken along its center line, with a tapered plate shown tensioned thereagainst. In this view a milling cutter is more or less diagrammatically illustrated in position to start the milling cut. The dotted line denotes the upper surface of the plate before the milling cut is made and the full line just below the dotted line indicates the upper surface of the plate after the milling cut is made;

Fig. 17 is a more or iessdiagrammatic view illustrating the manner of tensioning or pulling down the arched plate against the backing member;

Figs. 18 to 27 inclusive are transverse sections of the backing member or milling plate with the tapered plate shown tensioned thereagainst. |8-I8 to 21-21 ing plate is concerned, while the plate sections correspond to those of Figs. 5 to 14 respectively with the plate in' tensioned condition. The dotted lines denote the plate thickness before the milling operation. f

Fig. 28 is a typical transverse section of the vblade portion of the camber member blank after tllie same has been punched from the processed p ate;

' Fig. 29 is a view similar to that of Fig. 28 but represents a typical transverse section of the thrust plate blank after the same has. been punched from the processed plate;

Fig. 30 is a more or less diagrammatic view of a die press such as may be used in giving to the blanks the contour desired in the nished blade; and

Fig. 31 is a schematic view in transverse section of the iinished and die pressed camber member and thrust plate blanks in the position they are to occupy in the nished blade; the inlaid weld metal which bonds these into an integral structure as disclosed in said Dicks patent and my said applications having been omitted.

In making a camber member blank in accordance with the method of this invention, I longitudinally taper in thickness a relatively thin metal plate, such as plate 40 oi Figure 1. The taper extends throughout the major part of the length oi the plate or from the shank forming portion thereof to its The plate tapering tip end .42, is preferably accomplished by a milling operation which leaves relatively narrow side edge portions 43 and 44 of the origivnal plate thickness as shown in the drawings.

These upstanding edge portions are utilized in the operation of tensioning the plate against the backing member or milling plate preparatory to the finishing milling operation.

The longitudinally tapered plate is subjected to a die pressing operation, such as is more or less diagrammatically illustrated in Fig. 3. This pressing operation stresses the plate beyond its elastic limit and provides a mid section 45 which is transversely arched and which extends substantially throughout the length of the tapered portion of the plate, as shown in Fig. 4 and Figs. V5-14 inclusive. The pressing operation also bends portions 45 and 41 (located on opposite sides of arched mid section 45) down at relatively slight angles to the plane defined by the edges of said arched mid section as shown in said Figs. 3 and 4 and in Figs. 5-14 inclusive.

The dies 48 and .49 of the press (Fig. 3) are formed so as to overarch the central or mid section 45 since this portion tends to flatten somewhat when the dies of the press are separated.

The milling plate 50 used in carrying out the method of this invention has a longitudinally extending ilat mid section 5l, and side sections 52 and 53 which are inclined downwardly from section 5I to the lateral edges of the plate at relatively slight angles as shown in Fig. 17 and Figs. 20-27 inclusive. vIn outline, central section 5l is of the same shape as but slightly smaller than the body portion of the iinished blank and which is located within and bounded by the thick bordering edge portions hereinbefore referred to.

The upper surface 5I of the milling plate is inclined downwardly from about line 54 to its end 55 as shown in Fig. 16. This inclined por- `forming portion will clear the tion forms the support for shank forming portion 4I of the arched plate, and its inclination is provided so that when the arched plate is tensioned against the milling plate, said shank milling cutter during the milling operation. The milling plate adjacent its end 55 has'its upper surface inclined downwardly from about section line 21-21 to its end 55, as shown at 51, Fig. 16, so that when the arched plate is tensioned against the milling plate, its end above this inclined portion will bend down and also clear the milling cutter.

Arched portion 45 of the plate, with the convex side of the arched portion down, is placed above centrally located dat portion 5| of the milling plate or backing member 50. This member is bolted to the reciprocating bed of a horizontal milling machine V(not shown) equipped with hydraulically operated means, having hooked members 58 (Fig. 17) for hooking over upstanding edge portions 43 and 44 for tensioning the arched plate against the milling plate or backing member, or, in other words, for pulling all parts of the arched plate down into contact with the upper surfaces of themilling plate.

` These hooked members are arranged at short 69 and 10.

arched mid section of the plate to be flattened so that all parts of the same lie in metal-to-metal contact .with flat portion of the milling plate, and portions 46 and 41, located on opposite sides of the arched mid section, to lie in close contact with the upper surface of said side portions 52 and 53.

Shank forming portion 4| of the arched plate is pulled down to clear the milling cutter and tip portion 51 of the arched plate is also pulled down out of the way of the milling cutter.

The upper at surface of the longitudinally extending central portion 5| of the milling plate from about section line 21-21 to about section line 20--20 inclines downwardly at a slight angle to the horizontal.

After the plate has been pulled down in contact with the milling plate, the bed of the machine is slowlyl moved lengthwise below rotating milling cutter B0. This causes a straight milling cut to be taken not only throughout the length and breadth of that portion of tensioned plate 40 which lies above the ilat portion 5| of the milling plate, but also through the upper part of those portions 46 and 41 of the tensioned plate where those portions join the centralflattened portion 45. In other words, the milling cut taken throughout the length and breadth of the now flattened arched portion 45 extends a slight distance beyond the side edges of such flattened portion and into the side portions 46 and 41 of the plate as show n at 6| and 62 in Figs. 24-27 inclusive.

From this it will be seen that the flattened mid section of the tensioned plate, between its downwardly inclined ends is given an additional or nishing longitudinal taper which reduces the mid section of the plate to the thickness desired inthe finished blank and also reduces the thickness of those portions located at the junction of the flattened mid section and the offset side portions 46 and 41; those portions from which the thickened edge portions of the finished blank are formed. By reducing the thickness of those portions located at the junction of mid section 45 and the olset side portions 46 and 41, the change in thickness from that of the mid section to that of said side portions is made more or less gradual as shown at 63 and 64 in Fig. 28; this ligure representing a typical transverse section of the camber member blank after the same has been trimmed to the desired shape.

When the milling plate of Figs, 15 and 16 is to be used as the backing member for plate 40, the plate from which the camber member blank is to be formed, centrally located at portion 5| will have an outline substantially as dened by the solid line 65. When the milling plate is to serve as a backing member for plate 66 the plate from which the thrust plate, denoted by dotted outline 61, Fig. 2, is to be formed, it will have a centrally located at portion which is slightly modified in that at one end it. will be shortened as shown by dotted line 68 and at the opposite end narrowed as shown by dotted lines 'I'he plate may also be shortened for use in making thrust plate blanks by an amount equal to the distance between section lines |9-I9 and ends 55.

Dotted outline represents the outline of the camber member blank to be punched from plate 6B after finishing milling operation similar to that before referred to -is completed and before the blank has been die pressed to nished form.

In order to facilitate the tensioning operation,

the upstanding side portions 43 and 44 may if desired be sawed through at intervals as shown at 1|, 12 and 13.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In the manufacture of camber member and thrust plate'blanks for a hollow metal aircraft propeller blade, the steps which consist in longitudinally tapering throughout at least the major part of its length a relatively thin metal plate, in stressing at least the major part of the tapered part of said plate beyond its elastic limit to provide therein a longitudinally extending transversely arched mid section and side sections which are angularly disposed to the plane defined by the bordering edges of said arched mid section, in placing the convex face of said arched section against a backing member, in tensioning said plate againsty said backing member so that said arched section is reversely stressed and flattened into intimate contact with the backing member and so that said side sections are offset therefrom, in cutting material from the exposed face of the tensioned plate of said attened section, in trimming said plate and in pressing the same to form.

2. In the manufacture of a thrust plate blank for a hollow metal aircraft propeller blade, the

steps vwhich consist in longitudinally tapering in thickness a relatively thin metal plate, in stressing said plate beyond its elastic limit to provide a transversely arched longitudinally extending' mid-section, in placing the convex face of said arched section against a backing member, in tensioning said plate over the backing member to flatten said arched section into intimate consaid attened section, and in trimming said plate and in pressing the same to form.

3. In the manufacture of a camber member blank for a hollow metal aircraft propeller blade, the steps which consist in longitudinally tapering throughout at least the major part of its length a relatively thin metal plate, in stressing at least the major part of the tapered portion of said plate beyond its elastic limit to provide therein a longitudinally extending miusection which is arched transversely of the plate, and also to provide side sections which are angularly disposed to the plane defined by the bordering edges of said arched mid section, in placing the convex face of said arched section against a backing member, in so tensioning said plate against said backing member that said arched section is reversely stressed and flattened into intimate contact with the backing member and that said side sections are olset with relation thereto, in removing material from the exposed face ofthe plate at said attened section while vvtensioned, in trimming said plate and in pressing the same to form.

4. In the manufacture of camber member blank for a hollow aircraft propeller blade, the steps which consist in longitudinally tapering in thickness a-relatively thin metal plate throughout at least the major part of its length, in stressing said plate beyond its elastic limit to provide therein a transversely arched mid section which extends longitudinally of the plate throughout at least the major part of the length of its tapered portion, in placing the convex face of said arched ing cut along the to, but is smaller than the outline of the blade forming portion of the blank to be produced, in soy tensioning said plate against said backing member that said arched sectionis reversely stressed and flattened into intimate contact with the backing member, and that those portions of theplate on opposite sides of said mid section are offset from the plane of the so flattened mid section, in reducing the thickness of such fiattened section while tensioned by a straight millexposed face of the plate at said mid section, in trimming said plate to shape, and in pressing the trimmed plate to form.

5. In a method of making acamber member blank having bordering edge portions of materially greater thickness than the body of the blank intermediate said portions and with a portion intermediate said body and edge portions which gradually increases in thickness from said body to said edge portions, the steps which consist in longitudinally tapering a relatively thin metal plate throughout at least the major part of its length, in stressing the tapered portion of said plate beyond its elastic limit to provide a permanently transversely arched mid section having an outline corresponding to but slightly smaller than the outline of the body portion desired in the iinished blade, and to provide side sections which are angularly disposed to the plane defined by the bounding edges of said arched mid section, in placing the convex face of said arched portion in contact with the upper face of a backing member having a mid section which is fiat and which in outline corresponds to the outline of said arched section, in so tensioning said Vplate against said backing member as to flatten said arched section and provide a metal-to-metal contact between the same and the backing member throughout the entire area of said flattened section, in reducing the thickness of said flattened section throughout its length and breadth while the plate is tensioned by removing material Ifrom the exposed face thereof, and, in trimming the plate and in pressing the same to form.

6. In making a camber or thrust plate blank for a hollow metal aircraft propeller blade, the steps which consist -in transversely bending beyond its elastic limit and throughout at least the major part of its length a relatively thin metal plate to provide therein a longitudinally extending intermediate concavo-convex section, in placing the convex face of said section 'against the at face of a backing member with the side portions of said plate extended laterally beyond said at face, in so tensioning said blank against said backing member'that said concavo-convex part is made ilat, in taking a straight milling cut throughout the length and breadth of such tensioned atten'ed portion, in trimming the plate and in pressing the same to form.

7. In making a camber member blank for use in the manufacture of a hollow metal aircraft propeller blade, the steps which consist in longitudinally tapering a relatively thin metal plate throughout the major part of its length, in transversely bending the tapered portion of said plate beyond its elastic limit to form therein a longitudinally extending arched mld section, in placing the convex face of said arched mid section against the iiat upper face of a backing member with the portions on opposite sides of said rarched section extending beyond said fiat face, in tensioning said plate against said backing member so that said arched section is made flat, so that said side sections are offset belowsaid mid section and so that a portion of the thinner end of said plate is also offset below said fiat section, in taking a straight milling cut throughout the length and breadth of said tensioned flat section, in trimming said plate and pressing the same to form,

8. The method of graduating the thickness of a metal plate from a relatively thin central portion to a relatively thick edge portion which consists in deforming the plate to concavo-convex shape, locating the convex side o the plate over a substantially flat backing member, drawing the edges of the plate and backing member together by clamping means so that the plate and backing member are brought into intimate contact throughout their superposed areas, in machining a iiat on the exposed face of the plate, and in releasing said clamping means.

9. The method of graduating the thickness of a metal plate from a relatively thin central portion to a relatively thick edge portion which consists in deforming the plate to concavo-convex shape, locating the convex side of the plate over a substantially fiat backing member, drawing the edges of the plate and backing member together by clamping means so that the plate and backing member are brought into intimate contact throughout their superposed areas, in machining a flat on the exposed face of the plate, in releasing said clamping means, and in subsequently forming the plate to a cupped shape.

JAMES H. McKEE. 

